Abstract
Abstract. Geomagnetic field variations induce telluric currents in pipelines, which modify the electrochemical conditions at the pipe/soil interface, possibly contributing to corrosion of the pipeline steel. Modelling of geomagnetic induction in pipelines can be accomplished by combining several techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calculated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated using a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the frequency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observations made on a long pipeline in the auroral zone.Key words. Geomagnetism and paleomagnetism (geo-magnetic induction)
Highlights
Space weather produces geomagnetic disturbances that affect a variety of technological systems on the ground (Lanzerotti and Gregori, 1986; Boteler et al, 1998)
The pipe-to-soil potential (PSP) fluctuations interfere with pipeline surveys, which are made to check the integrity of the cathodic protection on the pipeline (Place and Sneath, 2001)
The results show the characteristic features that the largest pipe-to-soil potentials are produced at discontinuities in the pipeline, such as bends or the ends of the pipeline
Summary
Space weather produces geomagnetic disturbances that affect a variety of technological systems on the ground (Lanzerotti and Gregori, 1986; Boteler et al, 1998). A forward Fourier transform of the magnetic recordings is used to give the amplitude spectrum of the geomagnetic variations Multiplying this by the surface impedance, derived from a multi-layer Earth conductivity model, gives the amplitude spectrum of the electric field at the Earth’s surface. An infinitely long cylinder (ILC) model of the pipeline is used to determine how the presence of the pipeline modifies the electric fields in the nearby soil and in the pipe itself. Using magnetic data from a nearby recording site as an input to the model, calculations of the pipe-tosoil potential variations produced on a real pipeline in the auroral zone were made. Measurements of the pipe-to-soil potential variations were done in June 1998 as part of an international study of telluric effects on pipelines (Boteler and Trichtchenko, 2000). A comparison is made between the model results and the observed pipe-to-soil potentials
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